diff --git a/mozilla/content/html/document/src/nsHTMLDocument.cpp b/mozilla/content/html/document/src/nsHTMLDocument.cpp
index 0e7c51e634a..ab68d6ebac8 100644
--- a/mozilla/content/html/document/src/nsHTMLDocument.cpp
+++ b/mozilla/content/html/document/src/nsHTMLDocument.cpp
@@ -1344,9 +1344,13 @@ nsHTMLDocument::CreateElement(const nsAString& aTagName,
                               nsIDOMElement** aReturn)
 {
   *aReturn = nsnull;
+  nsresult rv;
 
-  nsresult rv = nsContentUtils::CheckQName(aTagName, PR_FALSE);
-  NS_ENSURE_SUCCESS(rv, rv);
+  // if we are in quirks, don't validate the tag name
+  if (mCompatMode != eCompatibility_NavQuirks) {
+    rv = nsContentUtils::CheckQName(aTagName, PR_FALSE);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }  
 
   nsAutoString tmp(aTagName);